Infections, in particular bacterial, pose a major threat to cancer patients as treatment related immuno-suppression and general weakness increase risk and severity of infections. Prompt identification of patients with a bacterial infection is necessary. Traditionally, fever, leucocytosis and elevated c-reactive protein (CRP) have been used in the evaluation in patients with suspected infection. How-ever, fever may be reduced by analgesics and steroids, leucocytes may be decreased due to anticancer therapy and CRP is in some cases elevated by the cancer disease as such. The diagnosis of bacterial infection is thus more difficult in cancer patients. Recently, pro-calcitonin (PCT) (her dækker maja's godt)